PROJECT SUMMARY This proposal seeks to evaluate the role of tissue sodium concentration (TSC), as measured by magnetic resonance imaging (MRI), on the acute management of brain ischemia. To achieve this goal, we will perform MRI scans within 20 minutes of recanalization therapy on acute stroke patients treated in the Interventional Neuroradiology service at the New York University School of Medicine (NYUSOM). Our underlying hypothesis is that brain tissue with a TSC above 65mM represents non-viable tissue and, therefore, will not recover upon reperfusion therapy of any type. This hypothesis was borne out from observations during our previous work on serial MR imaging during reversible middle cerebral artery occlusion of non-human primates. This hypothesis will be tested by comparing the spatially co-registered volume of critically elevated TSC (above 65mM) after recanalization and the volume of infarction (on the 30 day follow up) on the brain of each study subject. We plan to enroll a total of 120 subjects during this five-year proposal in order to account for the heterogeneity of the disease while still attaining the required statistical significance.